Electric Actuator with a Force/Pressure Measurement Sensor

ABSTRACT

An electric actuator for activating a valve device in the oil and natural gas industry, such as a slide valve, butterfly valve, ball valve, blow-out preventer or the like, has at least an actuator housing ( 3 ) that can be mounted to the valve device ( 2 ) and a displacement device ( 5 ) that is held within the actuator housing ( 3 ) and driven by means of an electric motor ( 4 ). In order, in the case of such an actuator, to register the forces or pressures that arise therein with both a static load or also with dynamic load changes reliably and with the exclusion of corresponding disturbance variables, and in order in this way to increase particularly the operational reliability of corresponding valve devices, at least one force/pressure measurement sensor ( 6, 7 ) is arranged between the actuator housing ( 3 ) and the displacement device ( 5 ). This sensor has, on its two interior facing sides ( 8, 9 ), two rings ( 11, 12 ) coated with a piezoresistive sensor layer ( 10 ) that forms one or more measurement surfaces ( 19 ), as well as at least one separating foil ring ( 13 ) arranged between these rings. A measurement voltage is applied between the separating foil ring ( 13 ) and a ring ( 11, 12 ) for determining a force/pressure-dependent resistance level.

BACKGROUND

In the oil and natural gas industry, a number of valve devices are known that are used in boreholes or in the conveyance of oil and natural gas. Examples of such valve devices are slide valves, butterfly valves, ball valves, blow-out preventers and the like. Such devices may be electrified and use electric actuators to activate the associated valve device. In particular, electrical actuators may be mounted to the valve devices from the outside by means of an actuator housing. A displacement device may be arranged within the actuator housing that is movably held in the actuator housing and that is driven by an electric motor. The displacement device has a dynamic connection to a corresponding valve element for displacement of the valve element between, for example, a closed and an open position. The electric motor can be a single motor or also a combination of two or more motors.

Such electric actuators are known, for example, from WO 2011/009471 and WO 2011/006519.

Considerable forces arise during the displacement of the valve elements by the displacement devices. Additional forces may arise if forces exercised by the conveyed oil or natural gas act on the actuator via the valve element and the displacement device. Because the displacement device is held in the actuator housing, the corresponding forces arise in a similar manner between the displacement device and the actuator housing mounted on the valve device.

Furthermore, other forces may arise if, for example, the corresponding valve element is driven into its seal seat when a valve is being closed, or a permanent sealing force is produced as an additional or resting force in such a sealing system. The forces can furthermore be influenced by frictional forces in the valve.

In accordance with various embodiments, an electric actuator registers forces and/or pressures that arise therein. These forces and/or pressures are registered both in the case of a static load and in the case of dynamic load changes. Additionally, the forces and/or pressures are registered reliably and with the exclusion of disturbance variables in order to increase the operational reliability of corresponding valve devices.

This object is solved by the features of the independent claims.

In accordance with various embodiments, at least one force/pressure measurement sensor is used that is arranged between the actuator housing and the displacement device. This sensor has, on its interior sides that face each other, two rings coated with a piezoresistive sensor layer that forms one or more measurement surfaces. A separating foil ring is arranged between these rings. A measurement voltage is applied between the separating foil ring and one of the rings for determining a force/pressure-dependent resistance level.

Because of the use of this force/pressure measurement sensor between the actuator housing and the displacement device, there results an arrangement in the corresponding flux of force so that the load acting on this system can be measured directly. This load results from the acting pressures or forces.

In this way, not only can the sensor make a precise measurement of a static load; it is also possible to register each dynamic load change, even if only small load changes arise.

This is an important difference with respect to customary piezo-elements for force or pressure measurement. Such piezo-elements allow a measurement only if, for example, charges are given off, i.e., if force changes change the electronic charge of the piezo-element. In the event of static loads without a load change, on the other hand, no signal is given off.

The combination of electric actuator and force/pressure measurement sensor of the above-described type makes it possible to measure forces directly in the drive of the actuator, and thus to measure real loads directly, particularly in the valve device activated by the actuator. This is important, for example, in electric blow-out preventers, in order to detect corresponding loading during the drilling process or during snubbing. Due to this determination of the forces or loads, it is also possible to minimize abrasion on the valve elements of the blow-out preventer or also on other valve devices and in this way, for example, to noticeably increase the operational reliability.

This also applies for the pressure or tensile forces produced during the opening or closing of a valve, which can be determined in real time according to embodiments of the present disclosure. This makes it possible to drive the corresponding valve element into its seat quickly and very sensitively and not only to generate a permanent sealing force as an additional or resting force in the corresponding sealing system, but also to be able to register these forces reliably at the same time. In this way, damage to the corresponding seal components in this area is reduced or eliminated, which increases valve longevity and reliability.

It is also possible to determine frictional forces in the valve or actuator during the activation of the valve device, likewise in real time, in addition to determining corresponding forces or pressures in the end positions of the corresponding valve device. This makes it possible to provide precise statements regarding the service life or maintenance cycle of such valve devices.

Because a corresponding measurement of force and pressure is possible throughout the entire activation of the valve device, frictional force/displacement diagrams can likewise be determined that can be measured directly at the valve element or via the displacement device. This means three-dimensional characteristic diagrams can be generated in real time during the operation of the corresponding valve device, whereby these characteristic diagrams allow precise service life statements to be made.

By means of the corresponding combination of actuator and force/pressure measurement sensor, it is also possible to determine collisions within the valve device or to detect a failure due to, for example, foreign bodies in the valve device. It must be noted in this connection that, for example, in the case of pipelines and the like, after their construction or also after corresponding repairs, residues of welding electrodes or the like can enter the sealing zones of slides or ball valves of the corresponding valve devices. Such foreign bodies can now be detected in these sealing zones and verified with regard to position, force/torque and pressure difference via the electric actuator, in particular, refer to electric motor and driven displacement device for information in this regard.

In order to be able to manufacture the thinnest possible piezoresistive sensor layers and consequently also thin sensors in general, it can prove advantageous if the piezoresistive sensor layer is a diamond-like carbon (DLC) layer. These layers have special characteristics with respect to hardness, friction coefficient and the like. Generally, the layers are amorphous and are manufactured, for example, by plasma-supported sputtering on the corresponding interior sides of the sensor rings. The layers continue to be flexible, so that given the corresponding flexibility of the sensor rings, the sensor as a whole can be formed in a flexible manner.

Such DLC layers are also used, for example, for increasing the resistance of steel or the like with respect to wear and tear, which is advantageous particularly in connection with use in the oil/gas industry. The high pressure resistance of such a layer is furthermore advantageous in this application area, because, for example, forces of up to 100 tons can arise in the corresponding valve devices.

In order to be able to arrange the sensors within the electric actuator at the corresponding locations in a simple manner, the rings can be formed as washers, particularly made of steel.

In this connection, it can furthermore be seen as advantageous if the separating foil ring is a steel foil ring. This can be manufactured by laser cutting, for example.

In order to allow electric contacting of the sensor in a simple manner, the separating foil ring can have a connecting contact that extends radially outward from the sensor. Naturally a plurality of these connecting contacts can also be provided. Contacting of the exterior surface of a corresponding ring can take place directly on the exterior surface.

In order to fashion the sensor with its different layers in a manner that is easier to handle and use, rings and separating foil ring can be connected to each other at their edges. An advantageous connection comes about by gluing, so that the sensor is correspondingly sealed with respect to the outside, which is advantageous in the case of use in the oil/natural gas industry and particularly in the case of maritime wells.

It is possible to coat the entire interior side of a corresponding ring with the sensor layer. In just the same way, it is possible for such a coating to be applied only on certain locations, in certain sectors or in areas of certain measurement surfaces that are separated from one another. In this way, sensor areas that are separated from one another can be formed. In addition to this formation and arrangement of the sensor layer, it is also possible to apply a further layer, for example with structuring for electric contacting, on the exterior side of a ring. The structuring for electric contacting can take place in this connection with regard to the different sensor areas or measurement surfaces. This means that different measurement surfaces or sensor areas can be contacted separately and used for measuring force/pressure.

It is likewise possible to provide the sensor layer itself with a further layer, such as, for example, a chromium layer, a doped layer, an insulation layer or the like, in order to protect this layer from external influences.

In accordance with various embodiments, the sensor has a layer composition that has a thickness of only a few millimeters, for example, 4 to 10 millimeters. As a result, the sensor can be inserted into the corresponding flux of force between the electric drive and valve element or the displacement device in different locations within the electric actuator.

Naturally an arrangement of a plurality of sensors at different locations is also possible.

As explained above, the sensor can be formed in a flexible manner. As a result, it can be adapted to the corresponding installation location even if there are curvatures in this area. This means that the sensor can do more than only measure force/pressure in a plane, which, for example, could be implemented by flat measurement surfaces of the force/pressure measurement sensor. Additionally, the sensor can also have a measurement surface or measurement surfaces arranged to extend in three dimensions and/or in space. As a result, the sensor is essentially independent of shape or support surface compulsions/requirements regarding its installation location. Measurements are made not only in flat areas, but also in three-dimensional areas, in a plurality of planes, in curvatures or along curvatures and, in particular, a plurality of measurement surfaces can be arranged along these areas, either connected to one another or separated from one another. This also applies analogously to measurement surfaces or sensor surfaces in the circumferential direction of the corresponding rings.

Force-selective measurement is possible due to this versatile manner of measurement. This makes it possible to eliminate disturbance variables that falsify the forces already in the sensor.

A possible arrangement of the sensor results by having this sensor allocated to a holding device for holding the displacement device in the actuator housing. Such a holding device is formed, for example, by tapered roller bearings or the like, whereby other mounts are also possible. It is likewise also possible, however, that the sensor is allocated to a support device for holding the displacement device in the actuator housing. For example, such a support device can be an at least partially circumferential projection on which the displacement device is supported within the actuator housing.

Further formations of such support devices are possible.

The described ring shape of the sensor results from the use of the electric actuator, in which, generally, the displacement device is a ball screw that is driven by one or more electric motors. In this case, the ball nut may be held in the actuator housing in such a manner that it can rotate, so that the corresponding recirculating ball spindle is displaced in the axial direction with the rotation of the nut. The corresponding forces are absorbed by the valve element and the recirculating ball spindle via the recirculating ball nut and transferred to the actuator housing. In this connection, ring shapes are conceivable that are formed with a circular, ellipsoid, generally oval or polygonal shape. It is likewise possible that the sensor has a discoidal shape. Other sensor shapes are within the scope of the present disclosure.

Due to the arrangement of the corresponding actuator particularly below sea level, generally there are no large temperature differences within the actuator. However, in order to be able to compensate for any temperature differences that do arise, a loaded and an unloaded measurement surface or a loaded measurement surface and a comparison surface separated from this measurement surface or surfaces can be used for measuring the resistance to allow for temperature compensation. This means, for example, that loaded and unloaded measurement surfaces are used for measuring the resistance and the temperature compensation then takes place on the basis of the corresponding measurement. In connection with the doped layers, it is also pointed out that it can also be advantageous if the sensor layer is doped directly to adjust its resistance.

The present disclosure particularly relates to a use of such a force/pressure measurement sensor in an electric actuator such as that which has been described. The present disclosure also relates to the corresponding features of the force/pressure measurement sensor as explained above and in further detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, advantageous embodiments of the invention are described in more detail using the figures included with the drawing.

Shown are:

FIG. 1: a longitudinal section through an embodiment of an electric actuator;

FIG. 2: a top view onto a force/pressure measurement sensor with a detail “X”;

FIG. 3: a side view of the force/pressure measurement sensor according to FIG. 2, and

FIG. 4: a side view similar to FIG. 3 for a further embodiment of a force/pressure measurement sensor.

DETAILED DESCRIPTION

Registering these forces or pressures that arise in real time disturbance variables that falsify the measurement of the forces and/or pressures. Such a force/pressure measurement sensor can be used for all electric actuators in the oil/natural gas industry. It can also be retrofitted to existing actuators and allows new control or detection options which have been explained above. A corresponding sensor furthermore requires only two electric connections, but no sealing and no kind of pressure encapsulation, for example, in the oil of the electric actuator, whereby pressure compensation with regard to the ocean depth pressure can be provided in the actuator by means of the corresponding oil pressure.

FIG. 1 shows a longitudinal section through an electric actuator 1 according to the application. One such electric actuator 1 is, for example, described in more detail in WO 2011/009471 and WO 2011/006519. The actuator 1 has at least an actuator housing 3, which is detachably mounted on one side to a valve device 2 partially shown in dashed lines. The actuator housing 3 has a plurality of parts that are connected to one another and that enclose an interior. A displacement device 5 is arranged in this interior. The displacement device 5 can be driven by an electric motor 4. For example, the electric motor 4 is formed as a step motor, whereby the stator is coupled to the actuator housing 3 and the rotor is coupled to the displacement device 5. A portion of the displacement device 5 is rotated by the rotor, whereby the displacement device 5 furthermore has a ball screw comprising a recirculating ball spindle 26 and ball nut 27. The ball nut 27 is rotated by the electric motor 4 by means of a rotating sleeve 28 and is held within the actuator housing 3 in a manner that does not allow axial/longitudinal displacement. Holding devices 21 and 22, in the form of tapered roller bearings, are used to rotate the corresponding rotating sleeve 28. At the same time, the rotating sleeve 28 is supported on the actuator housing 3 by means of these mountings. When the ball nut 27 rotates, the recirculating ball spindle 26 is displaced in the axial/longitudinal direction. The recirculating ball spindle 26 has a dynamic connection to a valve component of the valve device 2, which is not shown. The valve component is slid into its opened or closed position by means of axial displacement of the valve component.

The recirculating ball spindle 26 is connected to a pintle 29 by means of an adjustment head 25. The pintle 29 is connected to the valve component in a dynamic connection in a manner that is not shown.

Force/pressure measurement sensors 6 and 7 are arranged in the area of the rotating holder of the displacement device 5 on the actuator housing 3. These are constructed with a ring shape and installed in a pre-tensioned manner between the tapered roller bearings 21,22 and the actuator housing 3 for tension and pressure measurement. Corresponding electric connections are shown only in part, in particular in FIGS. 2-4.

In accordance with various embodiments, the corresponding sensors do not require sealing or pressure encapsulation in the oil of the actuator. In some cases, the oil of the actuator is used for compensating for the pressure of the ocean depth pressure.

A corresponding load flow of the tensile/pressure forces from the valve device 2 is effected going directly through the tapered roller bearings 21, 22 and over the sensors 6,7 on to the actuator housing 3. Thus, no force deflection occurs. In accordance with various embodiments, both static and dynamic forces/pressures are precisely and reliably registered, and in some cases are registered in real time.

In the depicted embodiment, the sensors are arranged between displacement device 5 and the actuator housing 3 and allocated according to the roller bearings 21, 22.

In other embodiment, the sensors 6, 7 may be allocated to a support device 23 of the actuator housing 3 for holding the displacement device 5 in the actuator housing 3.

The electric actuator 1 is only described as an exemplary environment for the use of the sensors 6, 7, although one skilled in the art appreciates that other embodiments are within the scope of the present disclosure. The use of the sensors 6, 7, as shown in the following figures, is applicable for the electric actuator as shown in FIG. 1 and also for electric actuators having different constructions or other devices where force/pressure measurement is needed. In some embodiments, electric actuators are used for displacing the valve components of corresponding valve devices in the oil/natural gas industry. Examples of such valves are slide valves, butterfly valves, ball valves, blow-out preventers or the like.

FIG. 2 shows a top view of a force/pressure measurement sensor 6, 7. The force/pressure measurement sensor 6, 7 is shown as a layered structure and is formed with a ring shape. The force/pressure measurement sensor 6, 7 can essentially be laid between corresponding parts of the electric actuator 1 in the manner of a washer, for example as shown in FIG. 1. The sensor 6, 7 has two stacked rings 11, 12, which are shown from the side view in FIGS. 3 and 4. The interior sides 8, 9 of the rings 11, 12 that face each other are coated with a piezoresistive layer as a sensor layer 10. The sensor layer 10 can cover the entire interior side 8, 9 of the corresponding sensor or ring 11, 12. Alternately, detail “X”, shows a localized coating as the sensor layer 10, which forms different sensor areas 20. These form corresponding measurement surfaces 19 for measuring a resistance in the area of the sensor area 20. The sensor areas 20 can have different shapes and can also be connected to one another, which allows force-selective measurement.

The corresponding shapes of the rings 11, 12 are congruent, with a separating foil ring 13 arranged between the rings 11, 12, as shown in FIG. 4. This separating foil ring 13 has at least one connecting contact 14 that extends radially outward. A measurement voltage can be applied to the connecting contact 14 and to an exterior side 16, 17 of one of the rings 11, 12. Due to the applied measurement voltage, a current flows through the sensor layer 10, and the resistance determined from the applied voltage and the resulting current depends on the force/pressure applied to the measurement sensor 6, 7. The piezoresistive sensor layer 10 on the interior sides 8, 9 of the rings 11, 12, which may be a piezoresistive layer, may be made of a diamond-like carbon layer, also called a DLC layer. This is a tribological layer with a high hardness level and low abrasion level. No distortion or deformation is needed for detecting force or pressure in the case of such a layer. Generally, a constant resistance is also applied in series with the corresponding sensor resistance.

Additional layers 24 can be applied on the interior sides 8, 9 or on the exterior sides 16, 17 of the rings 11, 12. The layers 24 can, for example, be formed from chromium, a doped material, an insulation material or the like. Furthermore, on the exterior sides 16, 17 of at least one of the rings 11, 12, a structure made of a conductive material can be arranged in order to supply the sensor areas or measurement surfaces with voltage. As a result, a separate measurement of each sensor area or each measurement surface can take place. The corresponding structures may, in some embodiments, be manufactured from chromium.

It is also possible to dope the sensor layer 10 directly in order to vary its resistance level.

In some embodiments, temperature compensation may take place if at least one further unloaded measurement surface is used to determine the resistance in addition to the loaded measurement surface or measurement surfaces of the sensor.

Referring back to FIG. 1, the corresponding sensors may be connected to one another along an edge 15, for example, by gluing.

A thickness 18 of the entire sensor 6, 7 lies in the range of a few millimetres, for example, in the range of 4 to 20 millimetres.

In the depicted embodiment according to FIG. 1, corresponding sensors in a ring shape are coupled directly to the tapered roller bearings as holding devices 21, 22 for tensile and pressure measurement and installed in a pre-tensioned manner. A measurement of the resistance of the sensors is made via the electric lines. Such a sensor needs no additional sealing and also no kind of pressure encapsulation in the oil of the actuator. A corresponding load flow of the tensile/pressure forces can be transferred directly through the sensors via the tapered roller bearing and into the actuator housing without any deflection. In this way, both static and dynamic forces/pressures can be registered precisely and reliably in real time. The sensor can also be coupled to a support device 23 within the actuator housing 3, if such a support device 23 is used for holding the displacement device 5.

FIG. 4 is a view similar to FIG. 3 for a further embodiment of the sensor. This differs from the sensor 6, 7 as shown in FIG. 3 in particular due to a multiple-part construction of the separating foil ring 13.

In FIG. 3, a one-piece separating foil ring 13 is used, while this is constructed of three adjacent rings in FIG. 4. The two outer rings are conductive rings with corresponding connecting contacts 14 that stick out radially outwards on opposite ends of the rings, also refer to the arrangement according to FIG. 2. An insulating ring in the form of an insulation foil ring, for example, made of plastic or the like, is arranged between these two conductive rings with connecting contact 14. This insulating ring is used for electrical insulation of the two other parts of the separating foil ring with connecting contacts 14. 

1. An electric actuator (1) for activating a valve device (2) in the oil and natural gas industry, comprising: an actuator housing (3) configured to mount to the valve device (2); a displacement device (5) held within the actuator housing (3) and driven by means of an electric motor (4); and a force/pressure measurement sensor (6, 7) arranged between the actuator housing (3) and the displacement device (5), the sensor comprising: two rings (11, 12), each having interior sides (8, 9) that face each other and exterior sides (16, 17) that face away from each other, wherein the rings (11, 12) are coated with a piezoresistive sensor layer (10) that forms one or more measurement surfaces (19); and a separating foil ring (13) arranged between the rings (11, 12), wherein a measurement voltage is applied between the separating foil ring (13) and one of the rings (11, 12) for determining a force/pressure-dependent resistance level.
 2. The electric actuator according to claim 1 wherein the piezoresistive sensor layer (10) comprises a diamond-like carbon layer.
 3. The electric actuator according to claim 1 wherein the rings (11, 12) comprise steel washers.
 4. The electric actuator according to claim 1 wherein the separating foil ring (13) comprises a steel foil ring.
 5. The electric actuator according to claim 1 wherein the separating foil ring (13) comprises a connecting contact (14) that extends radially outward.
 6. The electric actuator according to claim 1 wherein the rings (11, 12) and the separating foil ring (13) are connected to one another at their edges (15).
 7. The electric actuator according to claim 6 wherein the rings (11, 12) and the separating foil ring (13) are glued to one another at their edges (15).
 8. The electric actuator according to claim 1 wherein one of the sides (8, 9, 16, 17)/of one of the rings (11, 12) comprises a structure for electrical contacting and/or sensor areas (20) separated from one another.
 9. The electric actuator according to claim 1 wherein the force/pressure measurement sensor (6, 7) comprises a thickness of 4 to 10 millimeters.
 10. The electric actuator according claim 1 wherein the force/pressure measurement sensor (6, 7) comprises one or more flat measurement surfaces (19).
 11. The electric actuator according to claim 1 wherein the force/pressure measurement sensor (6, 7) comprises one or more measurement surfaces (19) that extend three dimensionally and/or are arranged in space.
 12. The electric actuator according to claim 1 wherein the force/pressure measurement sensor (6, 7) is coupled to a holding device (21, 22) configured to provide pivoting support for the displacement device (5) in the actuator housing (3).
 13. The electric actuator according to claim 1 wherein the force/pressure measurement sensor (6, 7) is coupled to a support device (23) configured to hold the displacement device (5) in the actuator housing (3).
 14. The electric actuator according to claim 1 wherein the ring (11, 12) of the force/pressure measurement sensor (6, 7) comprises a further coating on one of the/sides (8, 9, 16, 17), wherein the coating comprises at least one of chromium, a doped material, or an insulation material.
 15. The electric actuator according to claim 1 wherein the measurement surface (19) comprises a loaded measurement surface and an unloaded measurement surface or a loaded measurement surface and a comparison surface separated from the measurement surface , wherein a difference in resistance measurements of the loaded and unloaded measurement surfaces or the loaded measurement surface and the comparison surface can be used for temperature compensation.
 16. A method comprising: using a force/pressure measurement sensor (6, 7) in an electric actuator (1) for activating a valve device (2) in the oil and natural gas industry the force/pressure measurement sensor (6, 7) comprising two rings (11, 12) each having interior sides (8, 9) that face each other and a separating foil ring (13) arranged between the rings (11, 12), wherein the rings (11, 12) are coated with a piezoresistive sensor layer (10) that forms one or more measurement surfaces (19); applying a measurement voltage between the separating foil ring (13) and one of the rings (11, 12); and determining a force/pressure-dependent resistance level based on the applied voltage and a resulting current; wherein the electric actuator (1) comprises an actuator housing (3) configured to mount to the valve device (2) and a displacement device (5) held within the actuator housing (3) and driven by means of an electric motor (4); and wherein said sensor (6, 7) is arranged between the actuator housing (3) and the displacement device (5) for determining, via the displacement device, the pressure or force acting on the valve device. 